> Also, since the setup of the reparse header is such an underdocumented
> nightmare, please add as much commentary as possible around the choice 
> of allocations & offsets.

I'll try. It might turn into a novel.

> (BTW I'm not convinced that the PyMem change was the problem since 
> the PyMem_Raw* functions simply hand off to malloc/free unless
> there's a custom allocator.
> Unless of course the missing memset-0 was significant here).

I think it might be, there was a message in the log that DeviceIoControl failed:

  stty: standard input: Inappropriate ioctl for device

That could be attributed to garbage in the buffer.

I'll be back with a revised patch, and we can work from there. Thanks for your help!